This is the first in a series of proposed interlinked experiments on the human pharmacology of MDMA. We are interested in studying MDMA because of its popularity as a drug of abuse and to increase our understanding of MDMA's effects. We will determine pharmacokinetic effects and assess several pharmacodynamic effects. Subjects will be admitted to the GTCRC one day prior to dosing and will be monitored for 48 hours post dose. The services we will need from the GCRC include clinical admitting procedures, obtaining clinical lab samples on two of the three sessions as well as a daily urine toxicology screen for all three sessions, placement of an IV catheter each session, monitoring vital signs at least one time per shift, collecting, processing, and packaging study-mandated urine and blood samples, completing the NOSIE questionnaires once per shift, and administering several subject questionnaires. Performing these functions will aid in obtaining accurate study data which is vital for the successful completion of this study.